This invention is directed to an efficient manufacture of a covered elastic yarn. Covered elastic yarns are used today in body and leg support garments. The covered elastic yarns typically have a core material of spandex or other elastomer. Usually a single filament or monofilament comprises the core elastic element; however, more than one filament may be used. The wrapping element usually comprises several finer denier filaments, and the filaments are usually made from the same material as the support garment. The elastic yarn normally alternates with conventional inelastic yarns during the course of a material construction. Nylon polymer such as nylon 6 and nylon 6.6 is a popular support garment material for leggings, body stockings and the like.
There are a number of ways of "wrapping" the covering element onto the elastic core. It is known, for example, to pass the core yarn through a filament interlacing device. The covering filaments and core filament are intermingled as a result of a vortex action within the interlacing device and the two elements emerge from the intermixing device in an intermingled condition. During the wrapping operation, the core yarn is usually stretched from 3-5 times its relaxed length. The wrapping yarn is fed tensionless or "overfed" into the intermingling device; therefore, the wrapping or cover yarns tend to wrap around the core yarn and provide a covering therefore.
This invention is to a means for positioning covering filaments around a core yarn in a positive manner. Elastic core filaments are helically wrapped by an inelastic wrapping material. It is known to "single" and "double" wrap elastic yarns from, e.g. U.S. Pat. No. 4,150,529. This particular reference depicts double wrapping. The invention herein may be used in either process.
It is usual for covered yarn manufacturers to wind smaller packages from yarn producer prepared packages and utilize the smaller packages during core wrapping operations. This additional step, especially for higher speed wrapping operations (14,000 rpm and above), is required in view of the conventional producer packages having long winding stroke patterns. As the producer packages are formed, yarn is wound using strokes that generally carry the filament yarn being wound a substantial length of the package per package revolution. Such a package formation creates excessive tension variations when the yarn is being withdrawn in core wrapping operations; thus, the smaller formed packages as depicted in U.S. Pat. No. 4,150,529 and 4,232,507.
U.S. Pat. No. 4,435,952 and 4,484,433 depict the use of producer pirn packages in a wrapping operation for spun staple fibers. These references also depict the binding (wrapping) of a staple fiber in conjunction with the sliver forming process. The binding or wrapping in these references act more as a loose bind around the staple fibers and constitutes less than 5% per weight of the thread structure. Therefore, these references are not representative of a yarn covering process such as used in the formation of covered elastic yarns in support garments. The wrap count in the latter is much higher, permitting the wrapping yarn to substantially cover the elastic core in a relaxed condition.